'\" te
.\" Copyright 1989 AT&T.  Copyright (c) 2004, Sun Microsystems, Inc.  All Rights Reserved.
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.  See the License for the specific language governing permissions and limitations under the License.
.\" When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE.  If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner]
.TH MTMALLOC 3MALLOC "Mar 21, 2005"
.SH NAME
mtmalloc, mallocctl \- MT hot memory allocator
.SH SYNOPSIS
.LP
.nf
#include <mtmalloc.h>
cc -o a.out -lthread -lmtmalloc

\fBvoid *\fR\fBmalloc\fR(\fBsize_t\fR \fIsize\fR);
.fi

.LP
.nf
\fBvoid\fR \fBfree\fR(\fBvoid *\fR\fIptr\fR);
.fi

.LP
.nf
\fBvoid *\fR\fBmemalign\fR(\fBsize_t\fR \fIalignment\fR, \fBsize_t\fR \fIsize\fR);
.fi

.LP
.nf
\fBvoid *\fR\fBrealloc\fR(\fBvoid *\fR\fIptr\fR, \fBsize_t\fR \fIsize\fR);
.fi

.LP
.nf
\fBvoid *\fR\fBvalloc\fR(\fBsize_t\fR \fIsize\fR);
.fi

.LP
.nf
\fBvoid\fR \fBmallocctl\fR(\fBint\fR \fIcmd\fR, \fBlong\fR \fIvalue\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBmalloc()\fR and \fBfree()\fR functions provide a simple general-purpose
memory allocation package that is suitable for use in high performance
multithreaded applications. The suggested use of this library is in
multithreaded applications;  it can be used for single threaded applications,
but there is no  advantage in doing so. This library cannot be dynamically
loaded with \fBdlopen\fR(3C) during runtime because there must be only one
manager of the process heap.
.sp
.LP
The \fBmalloc()\fR function returns a pointer to a block of at least \fIsize\fR
bytes suitably aligned for any use.
.sp
.LP
The argument to \fBfree()\fR is a pointer to a block previously allocated by
\fBmalloc()\fR or \fBrealloc()\fR. After \fBfree()\fR is performed this space
is available for further allocation. If  \fIptr\fR is a null pointer, no action
occurs. The \fBfree()\fR function does not set \fBerrno\fR.
.sp
.LP
Undefined results will occur if the space assigned by \fBmalloc()\fR is overrun
or if a random number is handed to \fBfree()\fR. A freed pointer that is passed
to \fBfree()\fR will send a  \fBSIGABRT\fR signal to the calling process. This
behavior is controlled by \fBmallocctl()\fR.
.sp
.LP
The \fBmemalign()\fR function allocates \fIsize\fR bytes on a specified
alignment boundary and returns a pointer to the allocated block. The value of
the returned address is guaranteed to be an even multiple of \fIalignment\fR.
Note that the value of \fIalignment\fR must be a power of two, and must be
greater than or equal to the size of a word.
.sp
.LP
The \fBrealloc()\fR function changes the size of the block pointed to by
\fIptr\fR to \fIsize\fR bytes and returns a pointer to the (possibly moved)
block. The contents will be unchanged up to the lesser of the new and old
sizes. If the new size of the block requires movement of the block, the space
for the previous instantiation of the block is freed. If the new size is
larger, the contents of the newly allocated portion of the block are
unspecified. If \fIptr\fR is \fINULL\fR, \fBrealloc()\fR behaves like
\fBmalloc()\fR for the specified size. If \fIsize\fR is 0 and \fIptr\fR is not
a null pointer, the space pointed to is freed.
.sp
.LP
The \fBvalloc()\fR function has the same effect as \fBmalloc()\fR, except that
the allocated memory will be aligned to a multiple of the value returned by
\fBsysconf\fR(\fB_SC_PAGESIZE\fR).
.sp
.LP
After possible pointer coercion, each allocation routine returns  a pointer to
a space that is suitably aligned  for storage of any type of object.
.sp
.LP
The \fBmalloc()\fR, \fBrealloc()\fR, \fBmemalign()\fR, and \fBvalloc()\fR
functions will fail if there is not enough available memory.
.sp
.LP
The \fBmallocctl()\fR function controls the behavior of the \fBmalloc\fR
library. The options fall into two general classes, debugging options and
performance options.
.sp
.ne 2
.na
\fB\fBMTDOUBLEFREE\fR\fR
.ad
.RS 18n
Allows double  \fBfree\fR of a pointer.   Setting \fIvalue\fR to \fB1\fR means
yes and \fB0\fR means no. The default behavior of double \fBfree\fR results in
a core dump.
.RE

.sp
.ne 2
.na
\fB\fBMTDEBUGPATTERN\fR\fR
.ad
.RS 18n
Writes misaligned data into the buffer after \fBfree()\fR. When the buffer is
reallocated, the contents are verified to ensure that there was no access to
the buffer after the \fBfree\fR. If the buffer has been dirtied, a
\fBSIGABRT\fR signal is delivered to the process. Setting  \fIvalue\fR to
\fB1\fR means yes and \fB0\fR means no. The default behavior is to  \fInot\fR
write misaligned data.  The pattern used  is \fB0xdeadbeef\fR. Use of this
option results in a performance penalty.
.RE

.sp
.ne 2
.na
\fB\fBMTINITBUFFER\fR\fR
.ad
.RS 18n
Writes misaligned data into the newly allocated buffer. This option is useful
for detecting some accesses before initialization. Setting \fIvalue\fR to
\fB1\fR means yes and \fB0\fR means no. The default behavior is to \fInot\fR
write misaligned data to the newly allocated buffer. The pattern used is
\fB0xbaddcafe\fR. Use of this option results in a performance penalty.
.RE

.sp
.ne 2
.na
\fB\fBMTCHUNKSIZE\fR\fR
.ad
.RS 18n
This option changes the size of allocated memory when a pool has exhausted all
available memory in the buffer. Increasing this  value allocates more memory
for the application.  A substantial  performance gain can occur because the
library makes fewer calls  to the OS for more memory. Acceptable number
\fIvalue\fRs are between \fB9\fR and \fB256\fR. The default value is  \fB9\fR.
This value is multiplied by 8192.
.RE

.SH RETURN VALUES
.sp
.LP
If there is no available memory, \fBmalloc()\fR, \fBrealloc()\fR,
\fBmemalign()\fR, and \fBvalloc()\fR return a null pointer. When
\fBrealloc()\fR is called with \fIsize\fR > 0 and returns \fINULL\fR, the block
pointed to by \fIptr\fR is left intact. If \fIsize\fR, \fInelem\fR, or
\fIelsize\fR is 0, either a null pointer or a unique pointer that can be passed
to \fBfree()\fR is returned.
.sp
.LP
If \fBmalloc()\fR or \fBrealloc()\fR returns unsuccessfully, \fBerrno\fR will
be set to indicate the error.
.SH ERRORS
.sp
.LP
The \fBmalloc()\fR and \fBrealloc()\fR functions will fail if:
.sp
.ne 2
.na
\fB\fBENOMEM\fR\fR
.ad
.RS 10n
The physical limits of the system are exceeded by \fIsize\fR bytes of memory
which cannot be allocated.
.RE

.sp
.ne 2
.na
\fB\fBEAGAIN\fR\fR
.ad
.RS 10n
There is not enough memory available to allocate \fIsize\fR bytes of memory;
but the application could try again later.
.RE

.SH USAGE
.sp
.LP
Comparative features of the various allocation libraries can be found in the
\fBumem_alloc\fR(3MALLOC) manual page.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
MT-Level	Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR brk (2),
.BR getrlimit (2),
.BR dlopen (3C),
.BR malloc (3C),
.BR signal.h (3HEAD),
.BR bsdmalloc (3MALLOC),
.BR malloc (3MALLOC),
.BR mapmalloc (3MALLOC),
.BR umem_alloc (3MALLOC),
.BR watchmalloc (3MALLOC),
.BR attributes (7)
.SH WARNINGS
.sp
.LP
Undefined results will occur if the size requested for a block of memory
exceeds the maximum size of a process's heap. This information may be obtained
using  \fBgetrlimit()\fR.
